A heater device using an electrically conductive film as a planar heating element is known. Particularly, a heater device having a flexible, transparent, and electrically conductive film as a planar heating element is used as, for example, a defroster, a defogger or the like of a window or a display in an automotive vehicle, a building, a showcase, and various devices and/or facilities, and demand for the heater device is increasing as the applications thereof is being expanded.
A heater device applying as a planar heating element an electrically conductive material such as ITO (indium tin oxide) or PEDOT:PSS (poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate) which is conventionally used for transparent electrodes is known (Patent Literatures 1 and 2). In addition, graphene which is one of two-dimensional materials is transparent in the form of a single layer or several layers, and therefore a transparent electrode and a heater device using graphene are also known (Patent Literatures 3 and 4).